It is known to process municipal and household waste, and also some commercial waste and industrial waste which can be included in municipal waste, by treating the waste material in an autoclave. The waste material is introduced into an autoclave which is a closed pressure vessel, and is subjected to saturated steam at an appropriate pressure and temperature, typically of at least 3 bar and above 130° C. By processing the waste material under these conditions for a sufficient period of time, the waste material is sterilized making it safe to handle. Advantageously, organic material within the waste material, such as fibers, plant matters, paper and the like is broken down to form a mass of small cellulose particles. During the processing, labels and printings on metal waste, glass and plastic bottles are removed and any plastic items such as bottles reduce in size. The resulting material can be easily sorted to remove recyclable items, the cellulose particles may be used in a variety of different applications, and the remaining fraction which is sent to landfill will be less than about 20% of the original mass of waste material. The process of treating waste material in an autoclave has thus many advantages.
Some disadvantages of the method are known. The supply of heated arid pressurized steam to the autoclave requires a great deal of energy particularly over a sustained period. Further, the autoclave itself is a large and consequently heavy piece of equipment: a typical autoclave able to take 20 tons of waste will be 20 meters long by 3 meters in diameter. The autoclave is typically pivotally mounted and is raised to receive material waste and lowered during the treatment process and to permit removal of the treated waste from the autoclave. This requires an appropriately powerful lifting mechanism which must be able to support the autoclave and resist substantial sideways forces as a result of the rotation of the autoclave.
Some further disadvantages of the present method is that where an autoclave is loaded and unloaded through a common opening to the autoclave, there is a risk of cross contamination between treated and untreated waste material. The loading process can also be time consuming, for example where a conveyor is used to transfer waste into the autoclave through the autoclave mouth.